{"id":2467,"date":"2016-06-22T19:57:00","date_gmt":"2016-06-22T19:57:00","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/geologyxwaymakerxmaster\/?post_type=chapter&#038;p=2467"},"modified":"2023-08-14T22:11:35","modified_gmt":"2023-08-14T22:11:35","slug":"outcome-layers-of-the-geosphere","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/colorado-wmopen-geology\/chapter\/outcome-layers-of-the-geosphere\/","title":{"raw":"Layers of the Geosphere","rendered":"Layers of the Geosphere"},"content":{"raw":"<h2>Earth Layering:\u00a0 Compositions, Properties, Locations<\/h2>\r\nThe geosphere is a term used to describe the \"solid earth\" as a means to distinguish it from the hydrosphere (oceans) and the atmosphere.\r\nMost people recognize that Earth's interior has a kind of layered structure.\r\nHere, we'll learn about the classification of the various layers and their material composition;\u00a0 but a good question to keep in mind (we'll get to it eventually!) is simply why the earth (and other planets) are in fact layered as opposed to being homogeneous, and has the earth always been layered?\r\n<div class=\"textbox learning-objectives\">\r\n<h3>You\u2019ll Learn to<\/h3>\r\n<ul>\r\n \t<li>Understand the physical and chemical characteristics of the two types of crust<\/li>\r\n \t<li>Understand the physical and chemical characteristics of the mantle<\/li>\r\n \t<li>Understand the physical and chemical characteristics of both the inner and outer core<\/li>\r\n \t<li>Differentiate between the Lithosphere and the Asthenosphere<\/li>\r\n<\/ul>\r\n<\/div>\r\n<h2>Characteristics of the Crust<\/h2>\r\n<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/30154114\/image.png\"><img class=\"alignnone size-medium wp-image-3308\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/30154114\/image-300x225.png\" alt=\"\" width=\"300\" height=\"225\" \/><\/a>\r\n\r\n&nbsp;\r\n\r\nIn a nutshell (and it does kind of resemble a nut!)-- scientists have come to recognized three major compositional layers to planet earth.\u00a0 The outermost layer is the crust, atop which we live, and it is by far the thinnest.\u00a0 The crust varies in thickness, but it is only rarely more than about 50 km thick, which is nothing compared to the nearly 6370 km to earth's very center.\u00a0 In a volumetric sense, the crust is really a lot like the skin of an apple compared to the rest of the apple.\u00a0 We live on this \"skin,\" i.e. crust, but it really makes up very little of the whole earth!\r\n\r\nThe bulk of the earth is the mantle, which (contrary to popular belief) is nearly 100% solid rock (very little in the way of melt, or magma). \u00a0 There is a region in the upper mantle (around 100-250km in depth, but variable) where the mantle is near its melting temperature, and because of this it has rather mushy-gushy properties, like toothpaste or taffy or silly putty-- it's called the asthenosphere.\u00a0 The ductile properties of the asthenosphere are enormously important, because this allows the tectonic plates to slide around on top, resulting in the motions of plate tectonics!\r\n\r\nFinally, the deepest interior region is the core (made mostly of iron), separated into the outer core and inner core.\r\nIt's a clear separation, because the outer core is liquid and the inner core is solid.\r\nThis might seem kind of odd-- inasmuch as the outer core is actually cooler than the inner core.\r\n\r\nTemperatures in earth's center, the inner core, are in the range of 5000-6000 degrees C.\r\nBUT, due to such incredible pressure, the material (largely iron metal) is NOT liquid, but instead solid!\r\nThe outer core is somewhat cooler, but there is less pressure, and this allows the outer core (again, largely iron metal) to be in a liquid state!\r\n<span style=\"color: #ff00ff;\">Key Idea-- Melting Temperature is pressure dependent.\u00a0 Where the pressure is high, the melting temperature is also very high<\/span>.<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/24154840\/earth-int.jpg\"><img class=\"size-full wp-image-3547 alignleft\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/24154840\/earth-int.jpg\" alt=\"\" width=\"250\" height=\"292\" \/> \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 <\/a>\r\n\r\nOUTER CORE IS LIQUID METAL,, INNER CORE IS SOLID METAL!\r\n<div><\/div>\r\n&nbsp;\r\n\r\n&nbsp;\r\n\r\n&nbsp;\r\n\r\n&nbsp;\r\n\r\nOK, enough about the CORE,\r\nBack to Earth's CRUST\r\n\r\n<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/24155352\/cont-V-ocean-crust.gif\"><img class=\"alignnone size-medium wp-image-3548\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/24155352\/cont-V-ocean-crust-300x164.gif\" alt=\"\" width=\"300\" height=\"164\" \/><\/a>\r\n\r\nNote the two different types in image above, continental and oceanic.\u00a0 Earth\u2019s outermost zone, the crust, is thin and (compared to interior regions) relatively cold, and hence it behaves in a ridged fashion (rocks break more often than bend).\u00a0 a cold, thin, brittle outer shell made of rock.\r\n\r\nThere are two very different types of crust, each with its own distinctive physical and chemical properties, which are summarized in Table 1.\r\n<table>\r\n<thead>\r\n<tr>\r\n<th>Crust<\/th>\r\n<th>Thickness<\/th>\r\n<th>Density<\/th>\r\n<th>Composition<\/th>\r\n<th>Rock Types<\/th>\r\n<\/tr>\r\n<\/thead>\r\n<tbody>\r\n<tr>\r\n<td>Oceanic<\/td>\r\n<td>5\u201312 km (3\u20138 mi)<\/td>\r\n<td>3.0 g\/cm<sup>3<\/sup><\/td>\r\n<td>Mafic<\/td>\r\n<td>Basalt and gabbro<\/td>\r\n<\/tr>\r\n<tr>\r\n<td>Continental<\/td>\r\n<td>Avg. 35 km (22 mi)<\/td>\r\n<td>2.7 g\/cm<sup>3<\/sup><\/td>\r\n<td>Felsic<\/td>\r\n<td>All types<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<h3>Oceanic Crust<\/h3>\r\n<span style=\"float: none; background-color: #ffffff; color: #373d3f; cursor: text; font-family: 'proxima-nova',sans-serif; font-size: 16px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-decoration: none; text-indent: 0px;\">Usually, ocean crust is subducted at plate boundaries.\u00a0 There are, however, rare instances of oceanic crust being \"obducted\", in other words pushed on top of the continental crust.\u00a0 The pieces of ocean crust found sitting on continental crust are called ophiolites.\u00a0 This unusual occurrence provides geologists with a view of what a slice through the ocean crust might look like.\r\nSee below, a typical ophiolite sequence (\"top-down\" view):\r\n<\/span>\r\n\r\n[caption id=\"attachment_2495\" align=\"alignright\" width=\"350\"]<img class=\"wp-image-2495\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22202442\/gabbro.jpg\" alt=\"The gabbro is deformed because of intense faulting at the eruption site.\" width=\"350\" height=\"312\" \/> Figure 1. Gabbro from ocean crust[\/caption]\r\n\r\n<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/07142435\/Ophiolite.png\"><img class=\"alignnone wp-image-3532\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/07142435\/Ophiolite-110x300.png\" alt=\"\" width=\"167\" height=\"456\" \/><\/a>\r\n\r\n&nbsp;\r\n\r\n&nbsp;\r\n\r\n&nbsp;\r\n\r\nOceanic crust is composed of mafic magma that erupts on the seafloor to create basalt lava flows or cools deeper down to create the intrusive igneous rock gabbro (Figure 1).\r\n\r\nSediments, primarily mud and the shells of tiny sea creatures, coat the seafloor. Sediment is thickest near the shore, where it comes off the continents in rivers and on wind currents.\r\n\r\nThe oceanic crust is relatively thin and lies above the mantle. The cross section of oceanic crust in Figure 2\u00a0shows the layers that grade from sediments at the top to extrusive basalt lava, to the sheeted dikes that feed lava to the surface, to deeper intrusive gabbro, and finally to the mantle.\u00a0 This is basically the same thing as the ophiolite sequence, seen above!\r\n\r\n[caption id=\"attachment_2496\" align=\"alignnone\" width=\"302\"]<img class=\"size-full wp-image-2496\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22202533\/oceaniccrust.png\" alt=\"A cross-section of oceanic crust\" width=\"302\" height=\"500\" \/> Figure 2. A cross-section of oceanic crust.[\/caption]\r\n<h3>Continental Crust<\/h3>\r\n[caption id=\"attachment_2497\" align=\"alignright\" width=\"350\"]<img class=\"wp-image-2497\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22202631\/missourigranite.jpg\" alt=\"Granite from Missouri, and part of the continental crust\" width=\"350\" height=\"317\" \/> Figure 3. This granite from Missouri is more than 1 billion years old.[\/caption]\r\n\r\nContinental crust is made up of many different types of igneous, metamorphic, and sedimentary rocks. The average composition is granite, which is much less dense than the mafic rocks of the oceanic crust (Figure 3). Because it is thick and has relatively low density, continental crust rises higher on the mantle than oceanic crust, which sinks into the mantle to form basins. When filled with water, these basins form the planet\u2019s oceans.\r\n<h3>Summary<\/h3>\r\n<ul>\r\n \t<li>Oceanic crust is thinner and denser than continental crust.<\/li>\r\n \t<li>Oceanic crust is more mafic, continental crust is more felsic.<\/li>\r\n \t<li>Crust is very thin relative to Earth's radius.<\/li>\r\n<\/ul>\r\n<h3>Interactive Practice<\/h3>\r\nVisit <a href=\"http:\/\/www.learner.org\/interactives\/dynamicearth\/structure.html\" target=\"_blank\" rel=\"noopener\">Annenberg Learner-- cool site for investigating earth interior<\/a>\r\n<h2>Characteristics of the Mantle<\/h2>\r\n<div class=\"textbox shaded\">\r\n\r\n<b>A \"diamond delivery\" system?\u00a0 Sounds to good to be true!<\/b>\r\n\r\n<b><\/b><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23164600\/AL-on-KIMB.jpg\"><img class=\"alignnone size-medium wp-image-3544\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23164600\/AL-on-KIMB-300x226.jpg\" alt=\"\" width=\"300\" height=\"226\" \/>\u00a0 Alan Lester sitting on a KIMBERLITE outcrop, Green Mountain, Boulder, CO-- unfortunately, or perhaps fortunately (?),\u00a0 this local Boulder, Colorado, kimberlite does NOT contain diamonds.<\/a><img class=\"aligncenter wp-image-2499\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22203113\/diamonddelivery.jpg\" alt=\"A rough dark rock with diamonds embedded in it\" width=\"500\" height=\"318\" \/>\r\n<h2><span style=\"color: #ff0000;\">Named after TYPE LOCALITY in Kimberly, South Africa--\r\nKimberlite refers to a volcanic rock type that comes from relatively deep.\r\nKimberlite comes from the UPPER MANTLE.\r\n<\/span><\/h2>\r\nAs such, kimberlite eruptions bring pieces of the (relatively) deep earth.\u00a0 In the image above, we see a pretty green Cr-rich Spinel.\r\nBelow, a kimberlite containing a diamond inclusion!\r\n(Carbon is in its high pressure form, diamond, deep in earth!)\r\n\r\n<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/25024552\/diamond.jpg\"><img class=\"alignnone size-medium wp-image-3561\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/25024552\/diamond-300x225.jpg\" alt=\"\" width=\"300\" height=\"225\" \/><\/a>\r\n\r\nhttp:\/\/www.johnbetts-fineminerals.com\/jhbnyc\/mineralmuseum\/picshow.php?id=9027\r\n<h2>The details of kimberlite eruptions are not well understood.\r\nThey appear to have occurred more often when the earth was younger and hotter (a different \"geothermal gradient\").\r\nThey seem to be the result of melting due to the presence of CO2 rich fluids in the mantle-- with the eruptions taking melt from the mantle to the surface at very high velocities (originally thought to be near the speed of sound, but probably not quite that fast!).<\/h2>\r\n<\/div>\r\nTwo big ideas regarding the mantle:\r\n<ol>\r\n \t<li>\u00a0This is a region of very high temperatures and pressures.<\/li>\r\n \t<li>Although hot, for the most part the mantle is SOLID.\u00a0 Only in relatively rare locations does the mantle melt!\u00a0 (As you'll learn later-- it melts where it rises, e.g. mid-ocean ridges, and it melts where fluids lower the normally super-high temperatures required to melt rocks under pressure.<\/li>\r\n<\/ol>\r\n<h3>Solid Rock<\/h3>\r\n[caption id=\"attachment_2501\" align=\"alignright\" width=\"350\"]<img class=\"wp-image-2501\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22203311\/Peridotite.jpg\" alt=\"Peridotite is formed of crystals of olivine and pyroxene\" width=\"350\" height=\"233\" \/> Figure 4. Peridotite is formed of crystals of olivine (green) and pyroxene (black).\u00a0 Peridotite rock is often found as inclusions within Kimberlite.[\/caption]\r\n\r\nScientists know that the mantle is made of rock based on evidence from seismic waves, heat flow, and meteorites. The properties fit the ultramafic rock peridotite, which is made of the iron- and magnesium-rich silicate minerals (Figure 4). Peridotite is rarely found at Earth's surface.\r\n<h3>Heat Flow<\/h3>\r\nScientists know that the mantle is extremely hot because of the heat flowing outward from it and because of its physical properties.\r\n\r\nHeat flows in two different ways within the Earth:\r\n<ol>\r\n \t<li><strong>Conduction<\/strong>: Heat is transferred through rapid collisions of atoms, which can only happen if the material is solid. Heat flows from warmer to cooler places until all are the same temperature. The mantle is hot mostly because of heat conducted from the core.\u00a0 STICK A METAL ROD INTO A FIRE!<\/li>\r\n \t<li><strong>Convection<\/strong>: If a material is able to move, even if it moves very slowly, convection currents can form.<\/li>\r\n<\/ol>\r\nConvection in the mantle is the same as convection in a pot of water on a stove.\u00a0 SOUP RICE ANALOGY\r\n\r\nConvection currents within Earth's mantle form as material near the core heats up. As the core heats the bottom layer of mantle material, particles move more rapidly, decreasing its density and causing it to rise. The rising material begins the convection current. When the warm material reaches the surface, it spreads horizontally. The material cools because it is no longer near the core. It eventually becomes cool and dense enough to sink back down into the mantle. At the bottom of the mantle, the material travels horizontally and is heated by the core. It reaches the location where warm mantle material rises, and the mantle convection cell is complete (Figure 5).\r\n\r\n[caption id=\"attachment_1582\" align=\"aligncenter\" width=\"800\"]<img class=\"size-full wp-image-1582\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/05\/10205430\/Figure_6-8.jpg\" alt=\"In a convection cell, warm material rises and cool material sinks. In mantle convection, the heat source is the core. As the hot material rises and circles, the earth's crust moves. In the mid ocean ridge, two convection currents move the plates apart from each other in subduction.\" width=\"800\" height=\"345\" \/> Figure 5. Convection[\/caption]\r\n<h2>Characteristics of the Inner and Outer Core<\/h2>\r\n<div class=\"textbox shaded\">\r\n\r\n<strong>Do you want to take a journey to the center of the earth?<\/strong>\r\n\r\n<img class=\"aligncenter wp-image-2504\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22203500\/molten.jpg\" alt=\"Molten metal being poured from an extremely hot container\" width=\"500\" height=\"375\" \/>\r\n\r\nJules Verne's imagined core was fiery. But we know that the outer core is molten metal, as seen above. As hot as a journey to Verne's center of the earth might have been, a visit to the real location would be worse.\r\n\r\n<\/div>\r\n\r\n[caption id=\"attachment_2505\" align=\"alignright\" width=\"350\"]<img class=\"wp-image-2505\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22203558\/ironmeteorite.jpg\" alt=\"iron meteorite\" width=\"350\" height=\"281\" \/> Figure 6. An iron meteorite is the closest thing to the Earth\u2019s core that we can hold in our hands.[\/caption]\r\n\r\nAt the planet\u2019s center lies a dense metallic core. Scientists know that the core is metal because:\r\n<ol>\r\n \t<li>The density of Earth's surface layers is much less than the overall density of the planet, as calculated from the planet\u2019s rotation. If the surface layers are less dense than average, then the interior must be denser than average. Calculations indicate that the core is about 85% iron metal with nickel metal making up much of the remaining 15%.<\/li>\r\n \t<li>Metallic meteorites are thought to be representative of the core. The 85% iron\/15% nickel calculation above is also seen in metallic meteorites (Figure 6).<\/li>\r\n<\/ol>\r\nIf Earth's core were not metal, the planet would not have a magnetic field. Metals such as iron are magnetic, but rock, which makes up the mantle and crust, is not.\r\n\r\nScientists know that the outer core is liquid and the inner core is solid because:\r\n<ol>\r\n \t<li>S-waves do not go through the outer core.<\/li>\r\n \t<li>The strong magnetic field is caused by convection in the liquid outer core. Convection currents in the outer core are due to heat from the even hotter inner core.<\/li>\r\n<\/ol>\r\nThe heat that keeps the outer core from solidifying is produced by the breakdown of radioactive elements in the inner core.\r\n<h3 id=\"x-ck12-RXhwbG9yZSBNb3Jl\">Explore More<\/h3>\r\n<p id=\"x-ck12-NGVhM2JiYjNkNWFkOGFiMjAwZWI2YjQ5ZDc2OWMyM2E.-ro3\">Use this resource to answer the questions that follow.<\/p>\r\n\r\n<ol id=\"x-ck12-YjcyNjE5NTcyMWQwNmViODA4NzM1OGVkN2E3NjA3MTU.-fub\">\r\n \t<li>What materials can P-waves travel through?<\/li>\r\n \t<li>What materials can S-waves travel through?<\/li>\r\n \t<li>How do we know the outer core is liquid?<\/li>\r\n \t<li>What happens to P-waves when they go through a liquid?<\/li>\r\n \t<li>What do P-waves tell about the inner core?<\/li>\r\n<\/ol>\r\n<h2>The Lithosphere and Asthenosphere<\/h2>\r\n<h3><span style=\"color: #ff00ff;\"><strong>PLATE TECTONICS=&gt;<\/strong><\/span> this is just the motion of the outer portion of the earth (i.e. the lithosphere), sliding about, and carrying continents and also opening and closing ocean basins!\r\nPlate tectonics WORKS because the outer RIGID part of the earth is the Lithosphere.\u00a0 That's the part that moves -- see \"convection diagram\" above.\u00a0 <span style=\"color: #ff00ff;\">The lithosphere is the outermost (relatively cool) mantle and the crust.<\/span>\r\n<span style=\"color: #ff00ff;\">It slides around at velocities between 1 and 15cm per year.<\/span>\u00a0 Slow stuff, but over long periods of time can account for big changes in continental positions.\u00a0 (In general, plate velocities are on the order of about 5cm per year.)<\/h3>\r\n<span style=\"float: none; background-color: #ffffff; color: #373d3f; cursor: text; font-family: 'proxima-nova',sans-serif; font-size: 16px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-decoration: none; text-indent: 0px;\">RIGID block?\u00a0 What's that mean?\r\nAs per above, The lithosphere behaves like a rigid block.\u00a0 Push on any piece, and the other side of that piece moves!\r\nIn contrast, the asthenosphere is a bit more unusual.\u00a0 It's gushy.\u00a0 It's mushy.\r\nIn science-speak, the asthenosphere is a material that deforms in a plastic manner.\r\nIt's not a molten substance, merely something that lacks rigidity.\r\nExamples from our everyday life include toothpaste and (perhaps more everyday for kids) silly-putty!\r\n<\/span>\r\n<h3><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23163811\/sillyputty.jpg\">\u00a0\u00a0\u00a0<\/a><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23163811\/sillyputty.jpg\"><img class=\"alignnone size-full wp-image-3543\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23163811\/sillyputty.jpg\" alt=\"\" width=\"160\" height=\"240\" \/><\/a><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23163811\/sillyputty.jpg\"><img class=\"wp-image-2508 alignleft\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22203904\/toothpaste-745x1024.jpg\" alt=\"toothpaste\" width=\"224\" height=\"308\" \/><\/a><\/h3>\r\n<h3><\/h3>\r\n<h3><\/h3>\r\n<h3><\/h3>\r\n<h3><\/h3>\r\n<h3><\/h3>\r\n<h3>Lithosphere<\/h3>\r\nThe lithosphere is composed of both the crust and the portion of the upper mantle that behaves as a brittle, rigid solid. The lithosphere is the outermost mechanical layer, which behaves as a brittle, rigid solid. The lithosphere is about 100 kilometers thick. How are crust and lithosphere different from each other?\r\n\r\nThe definition of the lithosphere is based on how Earth materials behave, so it includes the crust and the uppermost mantle, which are both brittle. Since it is rigid and brittle, when stresses act on the lithosphere, it breaks. This is what we experience as an earthquake.\r\n\r\nAlthough we sometimes refer to Earth's plates as being plates of crust, the plates are actually made of lithosphere.\r\n<h3>Asthenosphere<\/h3>\r\nThe asthenosphere is solid upper mantle material that is so hot that it behaves plastically and can flow. The lithosphere rides on the asthenosphere.\r\n<h3>Summary<\/h3>\r\n<ul>\r\n \t<li>The lithosphere is the brittle crust and uppermost mantle.<\/li>\r\n \t<li>The asthenosphere is a solid but it can flow, like toothpaste.<\/li>\r\n \t<li>The lithosphere rests on the asthenosphere.<\/li>\r\n<\/ul>\r\n<h3>Explore More<\/h3>\r\nWatch this video.\u00a0 Think about how you might answers questions that follow--\r\n\r\nhttps:\/\/youtu.be\/hHteUIS0OFY\r\n<ol>\r\n \t<li>What does he mean by the mechanical properties of a layer?<\/li>\r\n \t<li>In the compositional model: What is the outermost layer? What are the two types of this layer and what are their main features?<\/li>\r\n \t<li>What is the lithosphere?<\/li>\r\n \t<li>What are the mechanical properties of the material below the lithosphere and what is the layer called?<\/li>\r\n \t<li>What is the composition and mechanical property of the mesosphere relative to the asthenosphere?<\/li>\r\n<\/ol>\r\n.\r\n\r\n&nbsp;","rendered":"<h2>Earth Layering:\u00a0 Compositions, Properties, Locations<\/h2>\n<p>The geosphere is a term used to describe the &#8220;solid earth&#8221; as a means to distinguish it from the hydrosphere (oceans) and the atmosphere.<br \/>\nMost people recognize that Earth&#8217;s interior has a kind of layered structure.<br \/>\nHere, we&#8217;ll learn about the classification of the various layers and their material composition;\u00a0 but a good question to keep in mind (we&#8217;ll get to it eventually!) is simply why the earth (and other planets) are in fact layered as opposed to being homogeneous, and has the earth always been layered?<\/p>\n<div class=\"textbox learning-objectives\">\n<h3>You\u2019ll Learn to<\/h3>\n<ul>\n<li>Understand the physical and chemical characteristics of the two types of crust<\/li>\n<li>Understand the physical and chemical characteristics of the mantle<\/li>\n<li>Understand the physical and chemical characteristics of both the inner and outer core<\/li>\n<li>Differentiate between the Lithosphere and the Asthenosphere<\/li>\n<\/ul>\n<\/div>\n<h2>Characteristics of the Crust<\/h2>\n<p><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/30154114\/image.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-3308\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/30154114\/image-300x225.png\" alt=\"\" width=\"300\" height=\"225\" \/><\/a><\/p>\n<p>&nbsp;<\/p>\n<p>In a nutshell (and it does kind of resemble a nut!)&#8211; scientists have come to recognized three major compositional layers to planet earth.\u00a0 The outermost layer is the crust, atop which we live, and it is by far the thinnest.\u00a0 The crust varies in thickness, but it is only rarely more than about 50 km thick, which is nothing compared to the nearly 6370 km to earth&#8217;s very center.\u00a0 In a volumetric sense, the crust is really a lot like the skin of an apple compared to the rest of the apple.\u00a0 We live on this &#8220;skin,&#8221; i.e. crust, but it really makes up very little of the whole earth!<\/p>\n<p>The bulk of the earth is the mantle, which (contrary to popular belief) is nearly 100% solid rock (very little in the way of melt, or magma). \u00a0 There is a region in the upper mantle (around 100-250km in depth, but variable) where the mantle is near its melting temperature, and because of this it has rather mushy-gushy properties, like toothpaste or taffy or silly putty&#8211; it&#8217;s called the asthenosphere.\u00a0 The ductile properties of the asthenosphere are enormously important, because this allows the tectonic plates to slide around on top, resulting in the motions of plate tectonics!<\/p>\n<p>Finally, the deepest interior region is the core (made mostly of iron), separated into the outer core and inner core.<br \/>\nIt&#8217;s a clear separation, because the outer core is liquid and the inner core is solid.<br \/>\nThis might seem kind of odd&#8211; inasmuch as the outer core is actually cooler than the inner core.<\/p>\n<p>Temperatures in earth&#8217;s center, the inner core, are in the range of 5000-6000 degrees C.<br \/>\nBUT, due to such incredible pressure, the material (largely iron metal) is NOT liquid, but instead solid!<br \/>\nThe outer core is somewhat cooler, but there is less pressure, and this allows the outer core (again, largely iron metal) to be in a liquid state!<br \/>\n<span style=\"color: #ff00ff;\">Key Idea&#8211; Melting Temperature is pressure dependent.\u00a0 Where the pressure is high, the melting temperature is also very high<\/span>.<a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/24154840\/earth-int.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-3547 alignleft\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/24154840\/earth-int.jpg\" alt=\"\" width=\"250\" height=\"292\" \/> \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 <\/a><\/p>\n<p>OUTER CORE IS LIQUID METAL,, INNER CORE IS SOLID METAL!<\/p>\n<div><\/div>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>OK, enough about the CORE,<br \/>\nBack to Earth&#8217;s CRUST<\/p>\n<p><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/24155352\/cont-V-ocean-crust.gif\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-3548\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/24155352\/cont-V-ocean-crust-300x164.gif\" alt=\"\" width=\"300\" height=\"164\" \/><\/a><\/p>\n<p>Note the two different types in image above, continental and oceanic.\u00a0 Earth\u2019s outermost zone, the crust, is thin and (compared to interior regions) relatively cold, and hence it behaves in a ridged fashion (rocks break more often than bend).\u00a0 a cold, thin, brittle outer shell made of rock.<\/p>\n<p>There are two very different types of crust, each with its own distinctive physical and chemical properties, which are summarized in Table 1.<\/p>\n<table>\n<thead>\n<tr>\n<th>Crust<\/th>\n<th>Thickness<\/th>\n<th>Density<\/th>\n<th>Composition<\/th>\n<th>Rock Types<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Oceanic<\/td>\n<td>5\u201312 km (3\u20138 mi)<\/td>\n<td>3.0 g\/cm<sup>3<\/sup><\/td>\n<td>Mafic<\/td>\n<td>Basalt and gabbro<\/td>\n<\/tr>\n<tr>\n<td>Continental<\/td>\n<td>Avg. 35 km (22 mi)<\/td>\n<td>2.7 g\/cm<sup>3<\/sup><\/td>\n<td>Felsic<\/td>\n<td>All types<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3>Oceanic Crust<\/h3>\n<p><span style=\"float: none; background-color: #ffffff; color: #373d3f; cursor: text; font-family: 'proxima-nova',sans-serif; font-size: 16px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-decoration: none; text-indent: 0px;\">Usually, ocean crust is subducted at plate boundaries.\u00a0 There are, however, rare instances of oceanic crust being &#8220;obducted&#8221;, in other words pushed on top of the continental crust.\u00a0 The pieces of ocean crust found sitting on continental crust are called ophiolites.\u00a0 This unusual occurrence provides geologists with a view of what a slice through the ocean crust might look like.<br \/>\nSee below, a typical ophiolite sequence (&#8220;top-down&#8221; view):<br \/>\n<\/span><\/p>\n<div id=\"attachment_2495\" style=\"width: 360px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2495\" class=\"wp-image-2495\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22202442\/gabbro.jpg\" alt=\"The gabbro is deformed because of intense faulting at the eruption site.\" width=\"350\" height=\"312\" \/><\/p>\n<p id=\"caption-attachment-2495\" class=\"wp-caption-text\">Figure 1. Gabbro from ocean crust<\/p>\n<\/div>\n<p><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/07142435\/Ophiolite.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-3532\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/07142435\/Ophiolite-110x300.png\" alt=\"\" width=\"167\" height=\"456\" \/><\/a><\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>&nbsp;<\/p>\n<p>Oceanic crust is composed of mafic magma that erupts on the seafloor to create basalt lava flows or cools deeper down to create the intrusive igneous rock gabbro (Figure 1).<\/p>\n<p>Sediments, primarily mud and the shells of tiny sea creatures, coat the seafloor. Sediment is thickest near the shore, where it comes off the continents in rivers and on wind currents.<\/p>\n<p>The oceanic crust is relatively thin and lies above the mantle. The cross section of oceanic crust in Figure 2\u00a0shows the layers that grade from sediments at the top to extrusive basalt lava, to the sheeted dikes that feed lava to the surface, to deeper intrusive gabbro, and finally to the mantle.\u00a0 This is basically the same thing as the ophiolite sequence, seen above!<\/p>\n<div id=\"attachment_2496\" style=\"width: 312px\" class=\"wp-caption alignnone\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2496\" class=\"size-full wp-image-2496\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22202533\/oceaniccrust.png\" alt=\"A cross-section of oceanic crust\" width=\"302\" height=\"500\" \/><\/p>\n<p id=\"caption-attachment-2496\" class=\"wp-caption-text\">Figure 2. A cross-section of oceanic crust.<\/p>\n<\/div>\n<h3>Continental Crust<\/h3>\n<div id=\"attachment_2497\" style=\"width: 360px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2497\" class=\"wp-image-2497\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22202631\/missourigranite.jpg\" alt=\"Granite from Missouri, and part of the continental crust\" width=\"350\" height=\"317\" \/><\/p>\n<p id=\"caption-attachment-2497\" class=\"wp-caption-text\">Figure 3. This granite from Missouri is more than 1 billion years old.<\/p>\n<\/div>\n<p>Continental crust is made up of many different types of igneous, metamorphic, and sedimentary rocks. The average composition is granite, which is much less dense than the mafic rocks of the oceanic crust (Figure 3). Because it is thick and has relatively low density, continental crust rises higher on the mantle than oceanic crust, which sinks into the mantle to form basins. When filled with water, these basins form the planet\u2019s oceans.<\/p>\n<h3>Summary<\/h3>\n<ul>\n<li>Oceanic crust is thinner and denser than continental crust.<\/li>\n<li>Oceanic crust is more mafic, continental crust is more felsic.<\/li>\n<li>Crust is very thin relative to Earth&#8217;s radius.<\/li>\n<\/ul>\n<h3>Interactive Practice<\/h3>\n<p>Visit <a href=\"http:\/\/www.learner.org\/interactives\/dynamicearth\/structure.html\" target=\"_blank\" rel=\"noopener\">Annenberg Learner&#8211; cool site for investigating earth interior<\/a><\/p>\n<h2>Characteristics of the Mantle<\/h2>\n<div class=\"textbox shaded\">\n<p><b>A &#8220;diamond delivery&#8221; system?\u00a0 Sounds to good to be true!<\/b><\/p>\n<p><b><\/b><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23164600\/AL-on-KIMB.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-3544\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23164600\/AL-on-KIMB-300x226.jpg\" alt=\"\" width=\"300\" height=\"226\" \/>\u00a0 Alan Lester sitting on a KIMBERLITE outcrop, Green Mountain, Boulder, CO&#8211; unfortunately, or perhaps fortunately (?),\u00a0 this local Boulder, Colorado, kimberlite does NOT contain diamonds.<\/a><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-2499\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22203113\/diamonddelivery.jpg\" alt=\"A rough dark rock with diamonds embedded in it\" width=\"500\" height=\"318\" \/><\/p>\n<h2><span style=\"color: #ff0000;\">Named after TYPE LOCALITY in Kimberly, South Africa&#8211;<br \/>\nKimberlite refers to a volcanic rock type that comes from relatively deep.<br \/>\nKimberlite comes from the UPPER MANTLE.<br \/>\n<\/span><\/h2>\n<p>As such, kimberlite eruptions bring pieces of the (relatively) deep earth.\u00a0 In the image above, we see a pretty green Cr-rich Spinel.<br \/>\nBelow, a kimberlite containing a diamond inclusion!<br \/>\n(Carbon is in its high pressure form, diamond, deep in earth!)<\/p>\n<p><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/25024552\/diamond.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-medium wp-image-3561\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/25024552\/diamond-300x225.jpg\" alt=\"\" width=\"300\" height=\"225\" \/><\/a><\/p>\n<p>http:\/\/www.johnbetts-fineminerals.com\/jhbnyc\/mineralmuseum\/picshow.php?id=9027<\/p>\n<h2>The details of kimberlite eruptions are not well understood.<br \/>\nThey appear to have occurred more often when the earth was younger and hotter (a different &#8220;geothermal gradient&#8221;).<br \/>\nThey seem to be the result of melting due to the presence of CO2 rich fluids in the mantle&#8211; with the eruptions taking melt from the mantle to the surface at very high velocities (originally thought to be near the speed of sound, but probably not quite that fast!).<\/h2>\n<\/div>\n<p>Two big ideas regarding the mantle:<\/p>\n<ol>\n<li>\u00a0This is a region of very high temperatures and pressures.<\/li>\n<li>Although hot, for the most part the mantle is SOLID.\u00a0 Only in relatively rare locations does the mantle melt!\u00a0 (As you&#8217;ll learn later&#8211; it melts where it rises, e.g. mid-ocean ridges, and it melts where fluids lower the normally super-high temperatures required to melt rocks under pressure.<\/li>\n<\/ol>\n<h3>Solid Rock<\/h3>\n<div id=\"attachment_2501\" style=\"width: 360px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2501\" class=\"wp-image-2501\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22203311\/Peridotite.jpg\" alt=\"Peridotite is formed of crystals of olivine and pyroxene\" width=\"350\" height=\"233\" \/><\/p>\n<p id=\"caption-attachment-2501\" class=\"wp-caption-text\">Figure 4. Peridotite is formed of crystals of olivine (green) and pyroxene (black).\u00a0 Peridotite rock is often found as inclusions within Kimberlite.<\/p>\n<\/div>\n<p>Scientists know that the mantle is made of rock based on evidence from seismic waves, heat flow, and meteorites. The properties fit the ultramafic rock peridotite, which is made of the iron- and magnesium-rich silicate minerals (Figure 4). Peridotite is rarely found at Earth&#8217;s surface.<\/p>\n<h3>Heat Flow<\/h3>\n<p>Scientists know that the mantle is extremely hot because of the heat flowing outward from it and because of its physical properties.<\/p>\n<p>Heat flows in two different ways within the Earth:<\/p>\n<ol>\n<li><strong>Conduction<\/strong>: Heat is transferred through rapid collisions of atoms, which can only happen if the material is solid. Heat flows from warmer to cooler places until all are the same temperature. The mantle is hot mostly because of heat conducted from the core.\u00a0 STICK A METAL ROD INTO A FIRE!<\/li>\n<li><strong>Convection<\/strong>: If a material is able to move, even if it moves very slowly, convection currents can form.<\/li>\n<\/ol>\n<p>Convection in the mantle is the same as convection in a pot of water on a stove.\u00a0 SOUP RICE ANALOGY<\/p>\n<p>Convection currents within Earth&#8217;s mantle form as material near the core heats up. As the core heats the bottom layer of mantle material, particles move more rapidly, decreasing its density and causing it to rise. The rising material begins the convection current. When the warm material reaches the surface, it spreads horizontally. The material cools because it is no longer near the core. It eventually becomes cool and dense enough to sink back down into the mantle. At the bottom of the mantle, the material travels horizontally and is heated by the core. It reaches the location where warm mantle material rises, and the mantle convection cell is complete (Figure 5).<\/p>\n<div id=\"attachment_1582\" style=\"width: 810px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-1582\" class=\"size-full wp-image-1582\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/05\/10205430\/Figure_6-8.jpg\" alt=\"In a convection cell, warm material rises and cool material sinks. In mantle convection, the heat source is the core. As the hot material rises and circles, the earth's crust moves. In the mid ocean ridge, two convection currents move the plates apart from each other in subduction.\" width=\"800\" height=\"345\" \/><\/p>\n<p id=\"caption-attachment-1582\" class=\"wp-caption-text\">Figure 5. Convection<\/p>\n<\/div>\n<h2>Characteristics of the Inner and Outer Core<\/h2>\n<div class=\"textbox shaded\">\n<p><strong>Do you want to take a journey to the center of the earth?<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-2504\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22203500\/molten.jpg\" alt=\"Molten metal being poured from an extremely hot container\" width=\"500\" height=\"375\" \/><\/p>\n<p>Jules Verne&#8217;s imagined core was fiery. But we know that the outer core is molten metal, as seen above. As hot as a journey to Verne&#8217;s center of the earth might have been, a visit to the real location would be worse.<\/p>\n<\/div>\n<div id=\"attachment_2505\" style=\"width: 360px\" class=\"wp-caption alignright\"><img loading=\"lazy\" decoding=\"async\" aria-describedby=\"caption-attachment-2505\" class=\"wp-image-2505\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22203558\/ironmeteorite.jpg\" alt=\"iron meteorite\" width=\"350\" height=\"281\" \/><\/p>\n<p id=\"caption-attachment-2505\" class=\"wp-caption-text\">Figure 6. An iron meteorite is the closest thing to the Earth\u2019s core that we can hold in our hands.<\/p>\n<\/div>\n<p>At the planet\u2019s center lies a dense metallic core. Scientists know that the core is metal because:<\/p>\n<ol>\n<li>The density of Earth&#8217;s surface layers is much less than the overall density of the planet, as calculated from the planet\u2019s rotation. If the surface layers are less dense than average, then the interior must be denser than average. Calculations indicate that the core is about 85% iron metal with nickel metal making up much of the remaining 15%.<\/li>\n<li>Metallic meteorites are thought to be representative of the core. The 85% iron\/15% nickel calculation above is also seen in metallic meteorites (Figure 6).<\/li>\n<\/ol>\n<p>If Earth&#8217;s core were not metal, the planet would not have a magnetic field. Metals such as iron are magnetic, but rock, which makes up the mantle and crust, is not.<\/p>\n<p>Scientists know that the outer core is liquid and the inner core is solid because:<\/p>\n<ol>\n<li>S-waves do not go through the outer core.<\/li>\n<li>The strong magnetic field is caused by convection in the liquid outer core. Convection currents in the outer core are due to heat from the even hotter inner core.<\/li>\n<\/ol>\n<p>The heat that keeps the outer core from solidifying is produced by the breakdown of radioactive elements in the inner core.<\/p>\n<h3 id=\"x-ck12-RXhwbG9yZSBNb3Jl\">Explore More<\/h3>\n<p id=\"x-ck12-NGVhM2JiYjNkNWFkOGFiMjAwZWI2YjQ5ZDc2OWMyM2E.-ro3\">Use this resource to answer the questions that follow.<\/p>\n<ol id=\"x-ck12-YjcyNjE5NTcyMWQwNmViODA4NzM1OGVkN2E3NjA3MTU.-fub\">\n<li>What materials can P-waves travel through?<\/li>\n<li>What materials can S-waves travel through?<\/li>\n<li>How do we know the outer core is liquid?<\/li>\n<li>What happens to P-waves when they go through a liquid?<\/li>\n<li>What do P-waves tell about the inner core?<\/li>\n<\/ol>\n<h2>The Lithosphere and Asthenosphere<\/h2>\n<h3><span style=\"color: #ff00ff;\"><strong>PLATE TECTONICS=&gt;<\/strong><\/span> this is just the motion of the outer portion of the earth (i.e. the lithosphere), sliding about, and carrying continents and also opening and closing ocean basins!<br \/>\nPlate tectonics WORKS because the outer RIGID part of the earth is the Lithosphere.\u00a0 That&#8217;s the part that moves &#8212; see &#8220;convection diagram&#8221; above.\u00a0 <span style=\"color: #ff00ff;\">The lithosphere is the outermost (relatively cool) mantle and the crust.<\/span><br \/>\n<span style=\"color: #ff00ff;\">It slides around at velocities between 1 and 15cm per year.<\/span>\u00a0 Slow stuff, but over long periods of time can account for big changes in continental positions.\u00a0 (In general, plate velocities are on the order of about 5cm per year.)<\/h3>\n<p><span style=\"float: none; background-color: #ffffff; color: #373d3f; cursor: text; font-family: 'proxima-nova',sans-serif; font-size: 16px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-decoration: none; text-indent: 0px;\">RIGID block?\u00a0 What&#8217;s that mean?<br \/>\nAs per above, The lithosphere behaves like a rigid block.\u00a0 Push on any piece, and the other side of that piece moves!<br \/>\nIn contrast, the asthenosphere is a bit more unusual.\u00a0 It&#8217;s gushy.\u00a0 It&#8217;s mushy.<br \/>\nIn science-speak, the asthenosphere is a material that deforms in a plastic manner.<br \/>\nIt&#8217;s not a molten substance, merely something that lacks rigidity.<br \/>\nExamples from our everyday life include toothpaste and (perhaps more everyday for kids) silly-putty!<br \/>\n<\/span><\/p>\n<h3><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23163811\/sillyputty.jpg\">\u00a0\u00a0\u00a0<\/a><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23163811\/sillyputty.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-3543\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23163811\/sillyputty.jpg\" alt=\"\" width=\"160\" height=\"240\" \/><\/a><a href=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/2666\/2016\/06\/23163811\/sillyputty.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-2508 alignleft\" src=\"https:\/\/s3-us-west-2.amazonaws.com\/courses-images\/wp-content\/uploads\/sites\/115\/2016\/06\/22203904\/toothpaste-745x1024.jpg\" alt=\"toothpaste\" width=\"224\" height=\"308\" \/><\/a><\/h3>\n<h3><\/h3>\n<h3><\/h3>\n<h3><\/h3>\n<h3><\/h3>\n<h3><\/h3>\n<h3>Lithosphere<\/h3>\n<p>The lithosphere is composed of both the crust and the portion of the upper mantle that behaves as a brittle, rigid solid. The lithosphere is the outermost mechanical layer, which behaves as a brittle, rigid solid. The lithosphere is about 100 kilometers thick. How are crust and lithosphere different from each other?<\/p>\n<p>The definition of the lithosphere is based on how Earth materials behave, so it includes the crust and the uppermost mantle, which are both brittle. Since it is rigid and brittle, when stresses act on the lithosphere, it breaks. This is what we experience as an earthquake.<\/p>\n<p>Although we sometimes refer to Earth&#8217;s plates as being plates of crust, the plates are actually made of lithosphere.<\/p>\n<h3>Asthenosphere<\/h3>\n<p>The asthenosphere is solid upper mantle material that is so hot that it behaves plastically and can flow. The lithosphere rides on the asthenosphere.<\/p>\n<h3>Summary<\/h3>\n<ul>\n<li>The lithosphere is the brittle crust and uppermost mantle.<\/li>\n<li>The asthenosphere is a solid but it can flow, like toothpaste.<\/li>\n<li>The lithosphere rests on the asthenosphere.<\/li>\n<\/ul>\n<h3>Explore More<\/h3>\n<p>Watch this video.\u00a0 Think about how you might answers questions that follow&#8211;<\/p>\n<p><iframe loading=\"lazy\" id=\"oembed-1\" title=\"Compositional and mechanical layers of the earth | Cosmology &amp; Astronomy | Khan Academy\" width=\"500\" height=\"281\" src=\"https:\/\/www.youtube.com\/embed\/hHteUIS0OFY?feature=oembed&#38;rel=0\" frameborder=\"0\" allowfullscreen=\"allowfullscreen\"><\/iframe><\/p>\n<ol>\n<li>What does he mean by the mechanical properties of a layer?<\/li>\n<li>In the compositional model: What is the outermost layer? What are the two types of this layer and what are their main features?<\/li>\n<li>What is the lithosphere?<\/li>\n<li>What are the mechanical properties of the material below the lithosphere and what is the layer called?<\/li>\n<li>What is the composition and mechanical property of the mesosphere relative to the asthenosphere?<\/li>\n<\/ol>\n<p>.<\/p>\n<p>&nbsp;<\/p>\n\n\t\t\t <section class=\"citations-section\" role=\"contentinfo\">\n\t\t\t <h3>Candela Citations<\/h3>\n\t\t\t\t\t <div>\n\t\t\t\t\t\t <div id=\"citation-list-2467\">\n\t\t\t\t\t\t\t <div class=\"licensing\"><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Original<\/div><ul class=\"citation-list\"><li>Introduction to Layers of the Geosphere. <strong>Authored by<\/strong>: Kimberly Schulte and Lumen Learning. <strong>Provided by<\/strong>: Lumen Learning. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by\/4.0\/\">CC BY: Attribution<\/a><\/em><\/li><\/ul><div class=\"license-attribution-dropdown-subheading\">CC licensed content, Shared previously<\/div><ul class=\"citation-list\"><li>Earth&#039;s Crust. <strong>Provided by<\/strong>: CK-12. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/www.ck12.org\/earth-science\/Earths-Crust\/lesson\/Earths-Crust-HS-ES\/?referrer=featured_content\">http:\/\/www.ck12.org\/earth-science\/Earths-Crust\/lesson\/Earths-Crust-HS-ES\/?referrer=featured_content<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC: Attribution-NonCommercial<\/a><\/em><\/li><li>Earth&#039;s Mantle. <strong>Provided by<\/strong>: CK-12. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/www.ck12.org\/earth-science\/Earths-Mantle\/lesson\/Earths-Mantle-HS-ES\/\">http:\/\/www.ck12.org\/earth-science\/Earths-Mantle\/lesson\/Earths-Mantle-HS-ES\/<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC: Attribution-NonCommercial<\/a><\/em><\/li><li>Earth&#039;s Core. <strong>Provided by<\/strong>: CK-12. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/www.ck12.org\/earth-science\/Earths-Core\/lesson\/Earths-Core-HS-ES\/\">http:\/\/www.ck12.org\/earth-science\/Earths-Core\/lesson\/Earths-Core-HS-ES\/<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC: Attribution-NonCommercial<\/a><\/em><\/li><li>Lithosphere and Asthenosphere. <strong>Provided by<\/strong>: CK-12. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"http:\/\/www.ck12.org\/earth-science\/Lithosphere-and-Asthenosphere\/lesson\/Lithosphere-and-Asthenosphere-HS-ES\/\">http:\/\/www.ck12.org\/earth-science\/Lithosphere-and-Asthenosphere\/lesson\/Lithosphere-and-Asthenosphere-HS-ES\/<\/a>. <strong>License<\/strong>: <em><a target=\"_blank\" rel=\"license\" href=\"https:\/\/creativecommons.org\/licenses\/by-nc\/4.0\/\">CC BY-NC: Attribution-NonCommercial<\/a><\/em><\/li><\/ul><div class=\"license-attribution-dropdown-subheading\">All rights reserved content<\/div><ul class=\"citation-list\"><li>INGE LEHMANN : How Inge Lehmann used Earthquakes to discover the Earthu2019s inner core. <strong>Authored by<\/strong>: Chandresh S. <strong>Located at<\/strong>: <a target=\"_blank\" href=\"https:\/\/youtu.be\/ELZ3B4flqNk\">https:\/\/youtu.be\/ELZ3B4flqNk<\/a>. <strong>License<\/strong>: <em>All Rights Reserved<\/em>. <strong>License Terms<\/strong>: Standard YouTube License<\/li><\/ul><\/div>\n\t\t\t\t\t\t <\/div>\n\t\t\t\t\t <\/div>\n\t\t\t <\/section>","protected":false},"author":17,"menu_order":2,"template":"","meta":{"_candela_citation":"[{\"type\":\"original\",\"description\":\"Introduction to Layers of the Geosphere\",\"author\":\"Kimberly Schulte and Lumen Learning\",\"organization\":\"Lumen Learning\",\"url\":\"\",\"project\":\"\",\"license\":\"cc-by\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"Earth\\'s Crust\",\"author\":\"\",\"organization\":\"CK-12\",\"url\":\"http:\/\/www.ck12.org\/earth-science\/Earths-Crust\/lesson\/Earths-Crust-HS-ES\/?referrer=featured_content\",\"project\":\"\",\"license\":\"cc-by-nc\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"Earth\\'s Mantle\",\"author\":\"\",\"organization\":\"CK-12\",\"url\":\"http:\/\/www.ck12.org\/earth-science\/Earths-Mantle\/lesson\/Earths-Mantle-HS-ES\/\",\"project\":\"\",\"license\":\"cc-by-nc\",\"license_terms\":\"\"},{\"type\":\"cc\",\"description\":\"Earth\\'s 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